Natural gas is a fossil fuel having comparatively low emissions of carbon dioxide (CO2) and comparatively low emissions of other waste products during burning. Its contribution as one of the most important energy resources in the world continues to increase. Against a background of raw material depletion, constantly increasing energy requirements and for reasons of environmental protection the treatment and utilization of natural gas thus represent a very promising possibility for efficient and low emission energy generation.
Accordingly the use of natural gas as fuel gas in gas turbines is also desirable in order thus to be able to generate electrical and mechanical energy in simple and cost-effective fashion. However, direct utilization of raw natural gas has hitherto been possible only to a limited extent on account of acidic constituents, such as in particular hydrogen sulfide (H2S). The trouble-free and energy-efficient operation of gas turbines requires limitation of the sulfur content in the fuel gas to avoid or at least reduce high temperature corrosion and also to comply with the globally tightened emissions limits concerning sulfur oxides (SOX). Hydrogen-sulfide-comprising fuel gases, and in particular acidic natural gases, must therefore be subjected to appropriate treatment.
For the separation of hydrogen sulfide from gases various separation techniques are known where physical or chemical absorption media, also known as scrubbing media, are employed to ensure the purities required for a further use of the particular gas. In addition to the classical absorption-desorption methods with subsequent H2S conversion, for example by means of a Claus process, so-called liquid-redox methods are employed in particular for smaller capacities.
These liquid-redox methods are based on the concept of the reactive absorption, i.e. a combination of absorption and oxidation. To separate the hydrogen sulfide from the particular gases the gas is brought into contact with a scrubbing medium and the hydrogen sulfide present in the gas is chemically or physically bonded to an active substance of the scrubbing medium. The fuel gas purified of hydrogen sulfide may then be burned in a gas turbine.
Treatment of the scrubbing medium comprising the hydrogen sulfide is effected subsequently via a redox agent which converts hydrogen sulfide present in the scrubbing medium into elemental sulfur and thus separates the hydrogen sulfide from the scrubbing medium. The redox agent is reduced by the hydrogen sulphide. By contacting with an oxygen-comprising gas the redox agent is reoxidized and accordingly regenerated. The feeding of oxygen-comprising gas is effected for example via blowers provided especially therefor or by gassing with externally supplied, precompressed oxygen-comprising air.